Super M hunting

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You want to LENGTHEN the rod if governor is too sensitive and surges, SHORTEN the rod if governor is slow to respond. This assumes all linkage/pins are snug and carb settings OK.

Hold that still if it still does it there is a passage plugged in the carb. My uncles H is doing that. I pulled the carb apart, and cleaned it then it ran fine for a while. Now a piece of crud is stuck somewhere in there again and it is back to doing it. His does it mid throttle and below. Wound up tight his is fine. Previous post is in the link.
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I've never worked on that type governor.

But is the adjustment you suggest to hold the carb against the idle stop when the dash lever is set at idle?

That is what I have found to cause idle surge, the governor still trying to control the speed at idle. which is not necessary.

Hunts, even when not at idle

(quoted from post at 19:41:44 06/29/21)

Click to expand...

Has it ever run right since you've had it?

Unless something is BADLY worn in the governor or linkage to the carb the "hunting" is most likely cause by a carburetor issue.

Under no load or light load, as the engine speed "catches up" with the governor setting the governor closes the throttle butterfly enough that the "load circuit" stops (or lessens) the flow of fuel and the "idle circuit" has to flow enough to make up for that.

When the engine slows a bit and the governor opens the throttle butterfly a bit the "load circuit" takes over again.

"Hunting" is the result of that transferring back and forth between the "idle" and "load" circuits not working as it's supposed to.

Some carbs (not sure about yours) have a "transfer circuit" and/or a "transfer passage" in the throttle bore next to where the butterfly is just above idle.

If the throttle shaft is loose in the carb body or if the throttle plate is not centered in the bore before it's attaching screws are tightened those can be contributing factors as they can affect the flow past the idle and/or transfer ports in the throttle bore.

Also, as I originally asked, has it ever run well since you've had it?

If NOT someone could have previously installed jets that are incorrect for this particular application.

I have seen a vacuum leak cause hunting. After swapping a different carburetor onto a lawn mower, it hunted badly. Found a vacuum leak between the carburetor and the manifold. Fixed that, and it ran like a top.